[1] A harvesting machine is configured to temporarily store crops that the harvesting machine has harvested from a farm field while travelling, in a crop tank.
Such a harvesting machine performs harvesting work on one or more farm fields by repeatedly storing crops in the crop tank and discharging crops from the crop tank. In a combine (one example of a harvesting machine) disclosed in JP 2011-036193A (Patent Literature 1), the mass of grain in the crop tank (the yield) is calculated when it has been determined that preparations for precise measurement have been completed, on the grounds that a predetermined period of time (e.g. 10 seconds) has elapsed since an orientation controller of the combine that uses a hydraulic cylinder determined that the orientation, in terms of the inclination, of a travelling machine body is horizontal relative to the right-left direction and the front-rear direction. Although such a combine can accurately measure the mass of grain in the crop tank, it takes a long time to prepare for precise measurement. Therefore, there is demand to perform simplified measurement as well, without preparing for precise measurement.
[2] JP 2014-068543A (Patent Literature 2) discloses a combine that includes: a grain tank that is mounted on a travelling machine body so that grain can be stored therein; and a load cell that measures the weight of the grain tank, and that can calculate the weight of crop in the grain tank. The combine according to Patent Literature 2 includes: the load cell that detects the weight of the grain tank; an inclination sensor that detects the inclination of the travelling machine body; and a yield measuring means that calculates the weight of crop based on a weight detection signal that is inputted from the load cell. In this regard, if the inclination of the machine body detected by the inclination sensor is within a permissible range, an instruction to calculate the weight of crop is outputted to the yield measuring means, and if the inclination of the machine body detected by the inclination sensor is out of the permissible range, the instruction to calculate the weight of crop is not outputted. The travelling machine body that is inclined is restored to the horizontal orientation upon a control instruction being outputted from an orientation correcting means to an orientation control apparatus. Patent Literature 2 discloses control in which whether or not the inclination of the machine body is within the permissible range is checked when the calculated yield is outputted, and if the inclination of the machine body is out of the permissible range, an instruction to restore the horizontal orientation is outputted to the orientation control apparatus.
With the load cell that measures the weight of the contents as well as the weight of the container, an error may occur in the results of measurement of the weight of the contents due to changes in the container over time and changes in a load cell attachment part over time. The zero point adjustment that is disclosed in JP 2009-264703A (Patent Literature 3) is effective for eliminating such an error. A load cell disclosed in Patent Literature 3 is for measuring the weight of a drying apparatus included in drying equipment, and is provided on the upper side of a frame member that is made of a sheet metal and that is fixed to the surface of the floor of a building. Therefore, this load cell is always maintained in the horizontal orientation unlike the load cell provided for the combine disclosed in Patent Literature 2 that can change orientation, and it is unnecessary to consider the inclination of the orientation in the zero point adjustment.
[3] As a combine that reaps stalks from a farm field and performs threshing while travelling, and measures the quality of grain when storing grain thus obtained in a grain tank, there is a conventional combine that is disclosed in JP 2013-118856A (Patent Literature 4).
In this combine, a receiving and holding part that makes a grain storage space for temporarily storing grain fed to a grain tank is formed, and the internal quality of grain that has been stored in the grain storage space is measured by an optical internal quality measurement apparatus. The bottom surface of the receiving and holding part is formed using a bottom plate (a shutter) that swings to open and close. Grain is temporarily stored when the bottom plate is in a closed state, and the grain temporarily stored is discharged when the bottom plate is in an open state. A supply (storage) state detection sensor that detects that a predetermined amount or more of grain has been stored is provided at an inner upper end portion of the receiving and holding part. In a lower area of the receiving and holding part, a grain presence (grain level) sensor that detects whether or not grain is present at the level of height of the grain presence (grain level) sensor is provided on a side wall of the crop tank, at a position that is slightly lower than the lower end position of the bottom plate in the open state. Measurement processing using the internal quality measurement apparatus is performed each time the supply state detection sensor detects that a predetermined amount or more of grain has been supplied to the receiving and holding part. Thereafter, the bottom plate is switched to the open state, and the grain is discharged. Then, the bottom plate is restored to the closed state again, and grain is stored. As a result of an increase in the amount of grain in the grain tank, the top end of the bottom plate is eventually embedded in the grain, and it becomes impossible to switch the bottom plate from the open state to the closed state. Therefore, measurement processing is cancelled upon the presence of grain being detected by the grain presence sensor.